Do you know the PPPOE workflow?

PPPoE Overview

PPPoEPoint-to-Point Protocol over Ethernet), that is, the Point-to-Point Protocol on Ethernet, which enables a host on the Ethernet to connect to the Internet through a simple access device, and control and manage the connected users.

PPPoE uses Client/Server). It encapsulates PPP packets in Ethernet frames to provide point-to-point connections over Ethernet.

PPPoE connection

PPPoE dial-up connections include Discovery and SessionPPP sessions. The two phases are described below.

Discovery stage

This phase is used to establish a connection. When a user host wants to start a PPPoE Session, the discovery phase must first be performed to identify the Ethernet MAC address of the PPPoE Server, and create a PPPoE Session ID ).

 

Basic workflow of the Discovery stage

As shown in, the Discovery stage consists of four steps. The following describes its basic workflow.

1. PADI: to establish a PPPoE connection, the PPPoE client sends a PADI (PPPoE Active Discovery Initiation) packet in broadcast mode. The PADI packet includes the Service requested by the client.

2. PADO: When the PPPoE server (BRAS) receives a PADI package, it determines whether it can provide services. If it can provide services, the PADO (PPPoE Active Discovery Offer) packet is sent to the client to respond. The PADO packet includes the PPPoE server name and the same service name as the PADI packet. If the PPPoE server cannot provide services for PADI, PADO packet response is not allowed.

3. PADR: Since PADI is sent as a broadcast, the PPPoE client may receive more than one PADO packet, it will review all received PADO packets, select a PPPoE Server Based on the server name or the provided service, and send the PADRPPPoE Active Discovery Request packet to the selected server. PADR data packets include the services requested by the client.

4. PADS: When the PPPoE server receives the PADR package sent by the client, it is ready to start a PPPoE session, which creates a unique PPPoE session ID for the PPPoE session, send the PADS (PPPoE Active Discovery Session-confirmation) package to the client as a response.

When the phase ends normally, both ends of the communication get the Session ID) and the MAC address of the other side. They define a unique PPPoE Session together.

PPP session phase

When PPPoE enters the PPP session phase, the client and server will perform standard PPP negotiation. After the PPP negotiation is passed, the data will be sent through the PPP encapsulation. As the Net Load of PPPoE frames, PPP packets are encapsulated in Ethernet frames and sent to the peer end of the PPPoE link. The Session ID must be the ID specified in the Discovery stage and remain unchanged during the Session. The MAC address must be the peer MAC address.

PPPoE disconnection

At any time in the session phase, the PPPoE server and client can send the PADTPPPoE Active Discovery Terminate packet to the other party to notify the other party to end the session. After receiving the PADT, you cannot use this session to send PPP traffic. After a PADT packet is sent or received, even the conventional PPP end packet cannot be sent. Generally, both parties use the PPP protocol to end the PPPoE session. However, when PPP cannot be used, PADT can be used to end the session.

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